1. Field of the Invention
The present invention pertains to flexible air ducting. More specifically, the present invention pertains to flexible ducting utilized for conveying air in heating and air conditioning systems.
2. Description of the Prior Art
Air conditioning systems for heating and/or cooling air are typically provided with cooling and heating equipment by which ambient air is heated or cooled depending upon the particular need. The heated or cooled air is then forced by an air handler of some type through air ducting for distribution to areas where needed, e.g. the rooms of a residence or building.
In the past, such ducting typically comprised passageways formed by sheet metal wrapped or covered with insulation. The use of sheet metal required construction to specific dimensions for moving the air from one point to another. Because of obstacles and space restrictions encountered, such construction could be very expensive.
In more recent times, flexible ducting has been developed to distribute air from an air handler to the areas needed. Typical flexible air ducting provides an inner liner of polyethylene or other plastic reinforced by a spirally wound coil member to form a passage through which air may flow. The plastic liner is basically a protective layer and the metal coil prevents the passage from collapsing and blocking air flow. Surrounding the inner liner is a layer, typically one inch to one and one-half inch, of fiberglass batting insulation material which provides resistance to heat transfer (R-value) between the conditioned air passing through the ducting and the unconditioned or ambient air surrounding the ducting. An outer layer of thin black polyethylene or thin reflexive sheathing material surrounds the layer of fiberglass batting material for the protection thereof. Flexible ducting is much more versatile than sheet metal ducts of the prior art and can be utilized with much less concern for obstacles, space limitations and specific dimensions. Flexible air ducting can be made in relatively long lengths. It may be easily cut with knives, scissors, and wire cutters to desired lengths and reconnected by clamps and duct tape.
It is, of course, important that ducting be insulated to prevent heat transfer between the air flowing through the ducting and the ambient air surrounding the ducting. That is a primary reason for the fiberglass batting layer which surrounds the inner liner of ducting of prior art. There are some significant safety and health concerns with fiberglass which has been identified as a possible carcinogenic. OSHA requires workers handling fiberglass insulation materials to wear protective clothing to prevent skin irritation. Workers are also required to wear respirator masks to keep from breathing fiberglass particles which break loose during handling. Workers must take care in cleaning up after work and special care is required in cleaning clothing worn during work. Since fiberglass batting insulation is made from tiny fibers of ground up glass held together with a binding substance, such concerns are warranted.
It is also very important that fiberglass particles not enter the air being distributed through the ducting. Although there is an inner liner of plastic and spiraled wire in air ducting of the prior art, the plastic may be punctured or torn relatively easily by technicians installing or servicing an air conditioning system. If, at some later date, a home owner or building owner has the ducting cleaned, cleaning brushes may also puncture the inner plastic liner. Of course, if the inner plastic liner is punctured, loose fibers of glass from the fiberglass batting insulation may be moved with air through the ducting and delivered or distributed into air breathed by home or building occupants. This, of course, may be hazardous to the occupants thereof. If a home or building is subsequently altered or demolished, disposal of fiberglass ducting may create contamination and ecological problems.
Better materials and composition of air ducting are needed. Compositions which would provide greater health and safety without sacrificing the flexible and versatile characteristics of flexible air ducting should be well accepted.
The present invention provides composite flexible air ducting which, as in the prior art, is provided with an elongated inner lining of plastic reinforced by a spirally wound coil member to provide an elongated continuous air passage. A layer of insulation surrounds the inner lining to provide thermal insulation of the air passage from ambient air and an outer sheath surrounds the layer of insulation to provide protection thereto. However, the layer of insulation provided in the flexible air ducting of the present invention is cotton batting or other natural fibrous materials which provide greater insulation and are much less hazardous than fiberglass batting of the prior art.
In addition, the outer protective sheath and the layer of natural fiber insulation of the present invention are uniquely bonded to each other by a layer of adhesive which, after application and curing, provides substantial thermal insulating properties. The preferred adhesive is a compound material of resins and ceramics which, when cured and hardened, has a substantial R-factor.
Thus, the present invention provides flexible air ducting with flexible and versatile characteristics of the prior art but with additional and improved characteristics. The natural fiber insulation eliminates the heath risk associated with fiberglass insulation of the prior art. Technicians manufacturing, installing or servicing the ducting are not required to wear protective clothing or respirator masks. No special clothing or cleaning of clothing and workers is required. Furthermore, the air ducting of the present invention provides substantially greater insulating qualities resulting in more efficient air handling systems, lower energy use and lower energy cost. It""s manufacture also requires less energy. Many other objects and advantages of the invention will be understood from reading the specification which follows in conjunction with the accompanying drawings.